The invention refers to a facility for needling of fleece by means of a needle bar holding at least one needle board, which is driven to and fro by means of an eccentric drive via axially displaceable pushing rods.
Since the stitching density at a given lifting frequency of the needle bar of a needling facility depends on the number of needles of the inserted needle board on the one hand, and on the rate of feed of the fleece to be needled on the other hand, the rate of feed of the fleece and thus the performance of the needling facility can be increased at a given stitching density by increasing the number of needles arranged in tandem in fleece feed direction. However, an extension of the length of the needle boards measured in fleece feed direction is prevented by the fact that the needle bar is supported at two axially displaceable pushing rods driven to and fro by means of an eccentric drive. These pushing rods are arranged in a row transverse to fleece feed direction, so that off-center loads of the needle board relative to fleece feed direction lead to tilting moments of the needle bar along the connecting axis of the contact points between the pushing rods and the needle bar. As these tilting moments must be reduced to an acceptable level, there is a limitation regarding the needle board length in fleece feed direction. Therefore, the only way to improve the performance of the needling machine is to arrange two needling facilities with one needle board, each, arranged in tandem, which makes the construction more complicated. Moreover, in case of needling facilities intended for patterned surface structures of the fleece, the possible shape of patterns is limited by the length of the needle board in fleece feed direction, because these patterns depend on the board surface available for distributing the needles. However, this limitation with respect to pattern cannot be evaded by arrangement of a successive needle board.
For jointly driving two needle boards arranged behind each other in fleece feed direction, reciprocating both in stitching direction and in fleece feed direction, the approach has been made (EP 0 892 102 A2) to arrange the needle bars of the two needle boards on one common rest, which is borne via the connecting rods of two eccentric shafts circulating in opposite directions, in some kind of four-bar mechanism. However, this acknowledged construction demands two needle boards with one needle bar, each.
Therefore, it is the purpose of this invention to design a facility for needling of fleece as described above, in such a way that the length of the needle board can be considerably extended in fleece feed direction without putting up with unfavourable consequences regarding construction.
The invention solves this task by fixing the needle bar at two rows of pushing rods arranged in tandem at some distance in fleece feed direction and connected via a crosshead, with the eccentric drive acting upon the crosshead.
Since the needle bar is not fixed in the conventional way at one row of pushing rods, but at two rows of pushing rods arranged in tandem at some distance in fleece feed direction, the torques effective on the needle board can be carried off easily to the pushing rods via the needle beams, because, in case of torque load of the needleboard, the pushing rods arranged at some distance to each other both in fleece feed direction and transverse to it are mainly subject to tensile and compressive stress. Thus is it easily possible to more than double the extension of the board in fleece feed direction compared with similar needle boards, so that the measures provided by the invention permit one correspondingly longer needle board in fleece feed direction, instead of a tandem arrangement of two needling facilities, which offers all the benefits gained by an extension of the board in fleece feed direction. To this end the pushing rods must be moved synchronously, which is easily achieved by connecting the rows of pushing rods via a crosshead, where the eccentric drive is effective.
The crosshead may be connected rigidly with the pushing rods, so that the crosshead is guided via the pushing rods proper. There is another possible construction by bearing the crosshead displaceable, parallel to the pushing rods, with the pushing rods articulated at the crosshead, leading to a favorable allowance compensation.